Many industrial and commercial processes utilise a process liquid that is partially or wholly miscible with water. It is often necessary to separate undissolved solids from a process liquid in which case the solids are typically removed as part of a slurry or sludge. If the slurry or sludge is valuable and/or requires additional treatment the presence of process liquid in the slurry or sludge can contaminate the slurry or sludge and/or cause difficulties with the additional treatment of the slurry or sludge. If, on the other hand, the slurry or sludge is unwanted and/or destined for disposal, the slurry or sludge is typically disposed of as waste material. The presence of valuable, noxious or toxic process liquids in the slurry or sludge can give rise to problems including                the release of potentially harmful substances into the environment,        the requirement to purchase process liquid to replace what has been lost with the slurry or sludge,        the requirement to purchase and operate complex equipment and systems to recover the process liquid from the waste slurry or sludge, and/or        inefficient energy use.        
It is an object of the present invention to overcome or substantially reduce in severity the above-mentioned difficulties or to at least provide the public with a useful alternative. More particularly, the present invention provides a process to separate one or more solids from a process liquid and an apparatus therefor, or to at least provide the public with a useful alternative.
An industrial application where these problems arise is in the removal of salt from glycol that is used for dehydrating gas and for preventing hydrate formation in oil and gas production facilities. The demineralisation is typically done by a flash vaporisation process in which a heated recycle liquid provides heat to vaporise an aqueous stream of glycol while collecting precipitated salt and other solid material in a liquid residue that can then be removed from the process. The processes described in the '802, '608, '373 and '208 patents each include a flash vaporisation process similar to the above and such flash vaporisation processes have been or are being applied in the oil and gas industry to remove unwanted salt from glycol. A shortcoming of each of these processes is that the waste residue containing unwanted solid material also typically contains a significant amount of glycol, leading to the abovementioned problems. To overcome these problems additional equipment such as settling tanks, centrifuges, filter presses, membranes, molecular sieves, and ion exchange devices have been installed, or considered for use, to reduce the amount of glycol that is disposed of with the waste material. For some applications settling tanks can be the simplest of these options, however sedimentation, which is what occurs within settling tanks, can only reduce the glycol content in the waste material by a limited degree. The other choices may offer better performance but usually at considerably higher cost and complexity.